Process plants, like those used in chemical, petroleum or other processes, typically include one or more process controllers communicatively coupled to at least one host or operator workstation and to one or more process control and instrumentation devices, such as field devices, via analog, digital or combined analog/digital buses. Field devices, which may be, for example valves, valve positioners, switches, transmitters, and sensors (e.g., temperature, pressure and flow rate sensors), perform functions within the process such as opening or closing valves and measuring process parameters. While a typical process plant has many process control and instrumentation devices, such as valves, transmitters, sensors, etc. connected to one or more process controllers which execute software to control these devices during the operation of the process, there are many other supporting devices which are also necessary for or related to process plant operation.
For example, many process plants have other computers which execute various host applications related to business functions, maintenance functions, configuration functions, diagnostic functions, etc. In particular, many process plants, and especially those which use smart field devices, use asset management applications to help monitor, track, and maintain the devices within the plant regardless of whether these devices are process control and instrumentation devices or are other types of devices. The Asset Management Systems (AMS) application sold by Emerson Process Management enables communication with and stores data pertaining to field devices to ascertain and track the operating status of various field devices.
Maintenance personnel who are responsible for ensuring that the actual equipment within the process is operating efficiently, and for repairing and replacing malfunctioning equipment, use host applications such as maintenance interfaces, the AMS application discussed above, and many other diagnostic applications to access information about the operating states of the devices within the process.
Generally, the various devices used in any particular process plant can be expected to be manufactured by a number of different manufacturers. Moreover, it is quite likely that not all of the devices communicate with each other or with the process control system in the same manner. To overcome the problem of incompatibility among devices provided by different manufacturers, the process instrumentation industry uses several standardized digital device communication protocols as defined or promulgated by various organizations, such as HART Communication Foundation, FOUNDATION™ Fieldbus, etc.
Typically, the communication protocols defined by these foundations include standards that specify how each device identifies itself and communicates with a process control system through the use of what is known as a device description (DD). Each device type typically has its own DD, which is a formal description of the data and operating procedures for a field device, including variables, methods, commands, menus and display formats associated with various features of the device. Information about every accessible variable of the device is generally included in the device description to thereby define the compatibility of and possible communications with the device. Such variables include, for example, process measurements, any derived values, and all the internal parameters of the device such as range, sensor type, choice of linearization, materials of construction, manufacturer, revision number, etc.
The DDs for various devices are typically used in a number of different manners. For example, when a process application or host application is implemented in a process plant, the maintenance personnel responsible for maintaining the process application may need to get help information about various parameters of various devices. Similarly, system designers writing a process application may use a DD to gain further information about a device. Device manufacturers generally provide DDs on a computer readable media so that these DDs can be easily copied into various process control system computers or into various process plant related applications. However, if a process application (such as a control, maintenance, diagnostic, configuration or other application) was developed before a particular device came into existence, the process application may not have access to the DD or other information about that device, which means that the process application will be unable to communicate with the device when the device is added to the process plant on which the application is used.